Molecular characterization of a cDNA encoding vitellogenin and its expression in the hepatopancreas and ovary during vitellogenesis in the kuruma prawn, Penaeus japonicus

In Crustacea, reproductive function and mechanisms regulating vitellogenesi s have not been fully elucidated. This is due in great part to a lack of in formation concerning the biochemical nature of the vitellogenin molecule, t he hemolymph precursor of yolk protein, vitellin, as well as the functional expression of the vitellogenin-encoding gene. We have therefore cloned a c DNA encoding vitellogenin in the kuruma prawn, Penaeus japonicus based on t he N-terminal amino acid sequence of the 91 kDa subunit of vitellin. The op en reading frame of this cDNA encoded 2,587 amino acid residues. This is th e first investigation reporting a full-length cDNA and its corresponding am ino acid sequence for vitellogenin in any crustacean species. Northern blot analysis and in situ hybridization have revealed that mRNA en coding vitellogenin was expressed in both the follicle cells in the ovary a nd the parenchymal cells in the hepatopancreas. In non-vitellogenic females , vitellogenin mRNA levels were negligible in both the ovary and hepatopanc reas, but in vitellogenic females, levels were dramatically increased in bo th tissues. In the ovary, highest levels were observed during the early exo genous vitellogenic stage, and thereafter rapidly decreased, whereas in the hepatopancreas, high levels were maintained until the onset of the late vi tellogenic stage. Differing profiles of vitellogenin mRNA levels in the ova ry and hepatopancreas suggest that the contribution of these tissues to vit ellogenin synthesis harbor separate and complementary roles during vitellog enesis.